1. Field of the Invention
The present invention relates to a magneto-optical head for data recording and/or reproduction on a magneto-optical recording medium and also to a magneto-optical storage device using this magneto-optical head.
2. Description of the Related Art
The optical head in a recent magneto-optical disk drive intended to realize size reduction is composed of a fixed optical assembly including a laser diode, a beam splitter for reflecting and transmitting a laser beam, and a photodetector for receiving reflected light from a magneto-optical disk, and a movable optical assembly including a carriage and an actuator mounted on the carriage and having an objective lens. The carriage is movable in the radial direction of the magneto-optical disk along a pair of rails by means of a voice coil motor (VCM).
A write-power laser beam emitted from the laser diode of the fixed optical assembly is first collimated by a collimator lens, next transmitted by the beam splitter, next reflected by a beam raising mirror of the actuator, and finally focused on the magneto-optical disk by the objective lens, thereby writing data onto the magneto-optical disk. On the other hand, data reading is performed by directing a read-power laser beam onto the magneto-optical disk. Reflected light from the magneto-optical disk is first collimated by the objective lens, next reflected by the beam splitter of the fixed optical assembly, and finally detected by the photodetector, thereby converting the detected magneto-optical signal into an electrical signal.
With a recent increase in amount of information covering image information inclusive of moving images, the size of a beam spot to be focused on a magneto-optical recording medium (magneto-optical disk) is required to become smaller, so as to realize high-density recording to the magneto-optical recording medium. Accordingly, the numerical aperture (NA) of the objective lens is increasing, and the operational distance of the objective lens from the magneto-optical recording medium is decreasing. Increasing the numerical aperture of a single objective lens is limited mainly because the manufacture of an aspherical single lens in the objective lens is limited. To achieve a high NA, a magneto-optical head using two lenses is disclosed in Japanese Patent Laid-open No. 2000-207797.
The magneto-optical head described in this publication is a magneto-optical head for a magneto-optical disk drive for recording by magnetic modulation, that is, a front illumination type magneto-optical head opposed directly to a recording layer of a magneto-optical disk. With respect to a glass plate on which a thin-film coil for generation of a magnetic field is formed, a first lens and a second lens are positioned in series on the side opposite to the coil forming surface. The first lens and the second lens constitute a two-component objective lens. The coil has a central opening.
A laser beam emitted from a light source such as a laser diode is first collimated by a collimator lens, next guided through a beam raising mirror to the objective lens, and next converged by the objective lens. Then, the laser beam having a fixed intensity is directed onto the magneto-optical disk. Simultaneously with this direction of the laser beam onto the magneto-optical disk, the coil formed on the glass plate is driven by a current modulated with data to be written, thereby effecting magnetic modulation to write the data onto the magneto-optical disk.
On the other hand, data reading is performed by directing a read-power laser beam onto the magneto-optical disk. Reflected light from the magneto-optical disk is first collimated by the two-component objective lens, next reflected by a beam splitter, and finally detected by a photodetector, thereby converting the detected magneto-optical signal into an electrical signal.
In the magneto-optical head described in this publication, the drive current for the coil is supplied through conductive patterns formed on both sides of a wiring member, so that the structure of current supplying means is very complicated. This complication is due to the fact that the wiring member is utilized as a heat dissipation path for dissipating the heat generated from the thin-film coil.